Controlled drive mechanism



Dec. 25, 1962 w. A. CARRINGTON ETAL' 3,069,911

CONTROLLED DRIVE MECHANISM Filed May 4, 1959 4 Sheets-Sheet 1 FIG. I.

CLUTCH CONTROLLER INVENTORS WILBUR A. CARRINGTON ALAN VAN BRONKHORSTATTORNEY Dec. 25, 1962 w. A. CARRINGTON ETAL 3,069,911

CONTROLLED DRIVE MECHANISM Filed May 4, 1959 4 Sheets-Sheet 2 FIG. 2.

I INVENTORS WILBUR A. CARRINGTON ALAN VAN'BRONKHORST ATTORNEY D 25, 1952w. A. CARRINGTON ETAL 3,069,911

CONTROLLED DRIVE MECHANISM Filed May 4, 1959 4 Sheets-Sheet 3 INVENTORWILBUR A. CARRING'F N BLAN VAN BRONKHORST Wig/aw ATTORNEY Dec. 25, 1962w. A. CARRINGTON ETAL. 3,069,911

CONTROLLED DRIVE MECHANISM Filed May 4, 1959 4 Sheets-Sheet -4 FIG. 5.

INVENTORS WILBUR A. CARRINGTON ALAN VAN BRONKHORST Y BMZW ATTORNEYBfihhfill Patented Dec. 25, 1 362 This invention pertains to acontrolled drive mechanism, and more particularly to a controlled drivemechanism which is adapted to store and deliver energy to an outputshaft.

In the inertial navigation art, it is customary to support stabilizedreference systems by means of a gimbal support. When stabilizedplatforms are supported by gimballed supports, the gimbals are usuallyservoed to maintain some desired angular relation between them. Thedrive means of the servo system is usually an electrical motor, althoughoccasionally it may be a pneumatic actuator or a hydraulic actuator.Whether the actuator which causes the gimbals to move is electrical,pneumatic or hydraulic, a flow of power to the actuator is necessary inorder to move the gimbals against their own inertia, friction, and thelike. Usually, the power requirements for causing the gimbals to rotatein their bearings is a modest one. However, upon occasion, it isnecessary to supply quantities of power which may be of the order of 10,20 or 100 times the average power requirement.

When an earth-level or space fixed reference system is supported by agimbal system in an aircraft, it is necessary to provide a gimbal systemwhich will not lock under any attitude of the aircraft. To preventgimbal lock, a convenient device that is frequently used is a fourth orredundant gimbal. It is readily evident that for a three degree offreedom system, only three gimbals are ordinarily required. However,when the axes of two of the gimbals are aligned, gimbal lock occursbecause the number of degrees of freedom of the gimbal system has beenreduced to two. it is customary, therefore, to supply a fourth orredundant gimbal so that the reference system continuously has at leastthree degrees of angular freedom.

in order to cause the redundant gimbal to follow a predeterminedalignment relative to the remaining gimbals, it is usual to servo theredundant gimbal. When the redundant gimbal follows a predeterminedalignment e ative to the remaining gimbals, under certain conditions itis necessary to slew the redundant gimbal through an angle of 180 in avery short period or" time, for example, a quarter of a second. Tofast-slew a redundant gimbal which has a high moment of inertia requiresa large impulse of torque.

This invention contemplates the use of a mechanical energy storingdevice such as (for example) a flywheel, to supply energy to theredundant gimbal to slew it 180 in a very short time without requiring alarge impulse of torque from the electric, pneumatic or hydraulicsystem. A flywheel or a rotating shaft is brought up to speed (forexample) by means of an electric, pneumatic or hydraulic motor. A pairof counter-rotating slip clutches is connected between the flywheel orhigh inertia shaft and the gimbal to be slewed. The slip clutches areadapted to be selectively energized to transmit the required amount oftorque in the required sense from the flywheel to the servoed gimbal.

It is not to be construed that the device of this invention is limitedin application to the servoing of a gimbal system. For example, thedevice of this invention could be utilized very nicely to position ananti-aircraft gun,

or the like. Consider an anti-aircraft gun which must slowly follow atarget and then suddenly change from one target to another in a fastmaneuver. If such a gun were electrically, hydraulically orpneumatically driven, a large surge of power would be required from thesource when the gun was rapidly slewed at a high angular rate unless themechanical storage device of this invention together with its associatedslip clutches were connected to drive such a gun mount.

Further, it is to be noted that in its broadest sense the servo of thisinvention is adapted to turn a shaft which is connected to any kind ofload whatsoever. The possible loads which may be driven by the device ofthis invention are too numerous to specifically mention,

It is, then, an object of this invention to provide .a novel servosystem.

it is another object of this invention to provide mechanical energystoring means adapted and connected to rotate a shaft.

It is still another object of this invention to provide means forslewing a gimbal.

it is yet another object of this invention to provide flywheel means,slip clutch connected to a shaft, to cause said shaft to rotate upon itsbearings.

Still another object of this invention may be envisioned as providing amachine, including a pair of electro-magnetic slip clutches connectedbetween a mechanical energy storing device and a gimbal to cause saidgimbal to selectively rotate in a predetermined direction by applying apredetermined amount and sense of torque to said gimbal.

Other objects will become apparent from the following description whentaken in connection with the accompanying drawings in which:

FiG. 1 shows a typical device of this invention connected to theredundant gimbal of a typical inertial reference device with thesupporting structure earth-level;

FIG. 2 is a diagam of an inertial reference device supported by astructure which is inclined 60 above the horizontal;

MG. 3 is a diagram of an inertial reference device with the axis of theredundant gimbal rotated through approximately 120;

FIG. 4 is a schematic diagram of a typical circuit which is adapted tocontrol a pair of slip-clutches which are positioned between amechanical energy storing device and an output shaft; and

HG. 5 is a side view, partially in section, of a magnetic particleslip-clutch which may be utilized in the deice of this invention.

In the figures, a typical inertial reference device ill (such as, forexample, a vertical gyroscope or a gyroscopically stabilized platform)is stably supported relative to a supporting frame or vehicle (such asan airframe) by means of a gimbal system 3d. The supporting frame orvehicle Ell is shown symbolically by the ground marks.

in the explanation of a typical use of the device of this invention, itis assumed that the supporting frame or vehicle is an airframe which hasa roll axis 17, a pitch axis and an azimuth axis normal to axes l5 and17.

inertial reference device ill is stabilized to remain angularly fixedrelative to the locally horizontal plane of the earth. inertialreference device ill also has three axes, viz, a roll axis 8, pitch axis15, and an azimuth F axis 13.

inertial reference device it; is mounted for freedom of rotation aboutazimuth axis ll upon bearings (not shown) which are attached to gimball2. Gimbal 12, in turn, is mounted for rotation about axis 8 (normal toaxis ll) relative to gimbal 14 upon shafts 9 and l3 and upon bearings(not shown). Gimbal id is mounted for rotation about pitch axis 15relative to gimbal l6 upon shafts l8 and l? and upon bearings (notshown). Gimbal 1&5 is mounted for rotation about axis 17 relative to thesupporting vehicle 25 upon bearings 21 and 2 Axis 17 is the roll axis ofthe supporting vehicle and is normal to pitch axis 15.

inertial element llll is de-coupled from supporting vehicle 20 throughgimbal system 3% by means of the usual system of angle detectors orpickoifs and torque motors (not shown).

in order to avoid gimbal lock, it is frequently desirable to drive afourth or redundant gimbal, such as, for example, gimbal is so that notmore than two gimbal axes ever coincide to leave at least three degreesof angular freedom.

In order to better understand the gimbal lock problem, suppose (forexample) that shafts and 19 were connected directly to airframe 2!}.When the supporting aircraft rolled about axis 3, gimbal 14 would startto turn relative to gimbal 12 about axis 17 upon shafts l3 and '9'. Ifthe aircraft 29 continued to roll about axis 37 until shafts l8 and It?were aligned with axis ll, the number of degrees of freedom of inertialsystem it would be reduced to two degrees and gimbal lock would occur.

An extra or redundant gimbal is supplied at 16 and is servoed to causeginibal lld to remain normal to gimbal 212 by the action of thecontrolled drive mechanism of this invention.

An electrical pickoff 22". is connected between the gimbals i2 and id togenerate a signal with the proper sense amplitude to provide a measureof the deviation from a right angle of the angle between gimbal l4 andgimbal l2. Pickoff 22 may be (for example) a synchro which generates nosignal when gimbals l2 and are normal to each other and which generatesa signal whose amplitude is a function of the magnitude of deviation ofsaid angle from a right angle and whose phase depends upon the sense ofsaid deviation.

To supply a torque in a controlled manner and sense to shaft 26,flywheel 28 is brought up to speed by means of a prime mover, such as(for example) electric motor 31 driven by electrical energy source 32.Alternatively, flywheel 28 may be brought up to speed and adapted toreceive its energy from a mechanical or hydraulic actuator (not shown).The device contemplated by this invention then utilizes an energystoring device 23 to supply torque to shaft 2d. It is to be noted thatmechanical energy storing device 28 under some circumstances may notactually be a separate mechanical element, but that the moment ofinertia of the motor shaft or other rotating mechanical element of theservo system may be utilized for this purpose. It is then intended thatwhen the word flywheel is used herein, that flywheel means a rotatingmember, having a relatively large moment of inertia, which is therebyadapted to store mechanical energy.

In the detailed mechanical connection of a typical device of thisinvention (shown more particularly in FIG. 1), flywheel 2-8 is geared orotherwise mechanically connected to cause input shafts ll and 43 to turnin counterrotating directions. Shafts and 43 are caused tocounter-rotate by means of shaft dd, gear 45, and by a pair ofcounter-rotating gears and 4-5 which engage gear 45 and which areconnected to drive shafts ll and 4-3, respectively. The input shafts ofclutches 35 and 37 then continuously rotate in opposite directions.

Clutches 35 and 37 are preferably of the magnetic particle slip clutchvariety, an example of which is shown in FIG. 5.

Alternatively, other kinds of mechanical clutches adapted to thisparticular servo system may be utilized.

When clutch 35 is energized, the output shaft thereof rotates gear in afirst direction, and when clutch 37 is energized, the output shaftthereof rotates gear 38 in a second direction opposite to said firstdirection.

Clutch controller 33 is connected between electrical angle detector 22and clutches and 37 to cause only one of said clutches to rotate itsoutput shaft at any particular time and to generate a torque at theoutput shaft whose magnitude and sense depends upon the signal receivedfrom clutch controller 33..

4 shows a typical clutch controller 33;. This particular clutchcontroller is intended to demonstrate only one of a number of possibleclutch controllers. The particular clutch controller which is shown (byway of only) in FIG. 4 is connected to be controlled by a iclcofl' orresolver of the synchro type wherein the phase of the output voltage ofresolver 22 depends upon the quadrant of the angle between gimbals l2and is t olitude of the output voltage generated s a function of thedeviation from a right angle c the angle between gimbals L. and Synchrois excited by source of voltage 6th which is also connected throughtransformer st to a demodulator d7.

Demodulator generates a constant voltage whose polarity depends upon thephase relation between the voltvoltage source 63 and the voltage outputof synchro The amp .ude of the direct voltage generated by atcr 57 isproportional to the amplitude of the alterna g outp t voltage fromsynchro 22.

The electrical output of demodulator 47 is connected to the input oftransistorized feedback amplifier 4-9 with a lag circuit in the feedbacknetwork to cause amplifier 49 to generate an output which is a functionof the input voltage and of the time derivative of the input voltage.

The electrical output of amplifier network 4? is connected to modulator51. The particular modulator which is shown in FIG. 4 is known as aring-bridge modulator. Construction and operation of modulator 51 isdescribed on page of Transistor Circuit Engineering (edited by R. F.Shea, third printing, copyright 1957 by John Wiley & Sons, Inc.)

The frequency of alternation of the electrical output of modulator 51 isthe same as the frequency of alternation of voltage source 64. Theoutput voltage of modulator 51 has an amplitude which is proportional tothe magnitude of the input voltage and has a phase which depends on thepolarity of the input voltage. The output of modulator 51 is connectedthrough transformer as to the input of clutch actuating network 53.

Clutch actuating network 53 is connected to clutches 35 and 37 toselectively control clutches 35 and 37 in accordance with the amplitudeof the voltage output of modulator 5i and with the relative phasebetween the voltage output of modulator Sit and the voltage of voltagesource In the particular circuit which is shown, a negative feedbacklead 55 is connected to the input center tap of transformer 66 tostabilize the system. Whether this lead is required depends upon theparticular transfer characteristics of clutches 35 and 37 as well as theservo transfer characteristics of the entire system.

Returning now to a detailed description of FIG. 4, first considerdemodulator "t7. Demodulator 47 is described briefly as a pair ofring-type phase sensitive demodulators 6S and 7d. Each demodulator is ahalf-wave demodula tor which operates over one-half cycle of the voltageof voltage source es. Each ring demodulator is identical. Demodulator ssis connected to operate over one-half cycle of the voltage of voltagesource as while demodulator '79 is adapted to operate over the otherhalf cycle. Terminals '72. and 74 are connected to opposite ends of theoutput of center tapped winding '76 of transformer 78, the center tap ofwhich is grounded and the primary of which is connected to the output ofsynchro 22. Ring demodulators 68 and 7d are in the form of a Wheatstonebridge. When the diodes of either demodulator are not firing, the armsof the bridge are open. When the diodes of one demodulator are fired orconducting, the Wheatstone bridge of that demodulator is balanced.Substantially no current is drawn from the circuit. Winding 86 oftransformer 62 is connected across the input of demodulator 68 atterminals 84 and 86 to cause diodes 88, 9d, 92, and 94 to conductthrough resistor 96 when the dotted end of winding is positive.Demodulator 68 acts then as a voltage dividing network in accordancewith Wheatstone bridge principles to cause terminal 93 to have the samepolarity and amplitude of voltage with respect to the ground terminal asappears at the terminal 72. A halfcycle later, ring demodulator 70operates to cause demodulator 47 to be a full wave phase sensitivedemodulator.

The full wave pulsed voltage which appears at terminal 93 is smoothed bymeans of a smoothing network of a choke coil tilt) and a by-passcondenser 102. The electrical output then of full wave demodulator 47depends upon the amplitude and phase of the output voltage of synchro22. When the voltage of winding 76, in accordance with the usual dotconvention, is in phase with the voltage of voltage source 6%, theelectrical output of demodulator d? is positive. When the voltage ofwinding 76 is opposite in phase to the voltage of voltage source on, theelectrical output. of demodulator 47 is negative.

The construction and operation of amplifier 4? is described generally inan article by Dean W. Slaughter which appears in the May 1955 issue ofElectronics magazine at pages 174 and 175 entitled, Feedback- StabilizedTransistor Amplifier. Feedback amplifier 49 utilizes five transistorsand a feedback lag network.

in FIG. 4-, a positive source of voltage (not shown) is connected toterminal 13% to place the proper operating potential on the base andcollector of transistors N3, 114, 122, and on the collector oftransistors 104, 15.

A negative potential source (not shown) is connected to terminal 134 toplace the proper operating potential on the emitter of transistors itid,115, and on the base of transistor 122.

A second negative potential source (usually of different magnitude,depending upon the characteristics of the respective transistor) isconnected to terminal 132 and to the emitter of transistor T22.

Emitters of transistors 1th and 114 are connected through resistor lidto the ground terminal, which is of a negative potential.

The collector of transistor 122 is connected through a filter network ofresistors 138, let 142, and condenser Md, and equalizing condenser 136to the base of transistor 315'.

The signal is now traced through amplifier 49. Consider (for example)that a positive signal is applied to the base of transistor 1 34.Assuming further that the emiter voltage of transistor Hi4 remainsconstant, the collector of transistor 1M then becomes negative whichplaces a negative signal on the base of transistor The negative signalon the base of transistor 168 causes a negative signal to appear at theemitter of transistors wt; and 114;- inasmuch as the collector oftransistor 18?: is maintained at a constant potential. It is furtherassumed that the base of transistor 11 iis maintained at a constantpotential. A negative signal applied to the emitter of transistor 114causes a negative signal to appear on the collector of transistor 2114which, in turn, is coupled through resistor 138 to the base oftransistor 122. The emitter of transistor 122 is maintained at aconstant potential so that a negative potential applied to the base oftransistor 122 causes a positive potential to appear at the collectorthereof. The collector of transistor T22 is the output terminal ofamplifier 49.

A feedback loop is also connected between the output of the collector oftransistor T22 and the base of transistor I115. Coupling condenser 136acts as a neutralizing condenser to reduce stray oscillation in thecircuit. The T network (of resistors 14%) and M2 shunted by the seriescombination of condenser 146 and resistor 144) in parallel with resistor138 is a frequency sensitive lag network,

the values of the components of which are determined in accordance withthe desired speed of response of the entire servo network. It is wellknown in the art that a lag network in the feedback branch of a feedbackamplifier causes the feedback amplifier to act as if it has a leadnetwork in series therewith.

The electrical output at the collector of transistor T22, is connectedthrough resistor to the center tap of the winding 159 of transformerWinding 15f; is connected through transformer 152 to voltage source 64.Ringbridge modulator 5]. then is biased by the direct current voltageapplied to the center tap of winding The electrical output of modulator51 is an alternating voltage whose phase depends upon the polarity ofthe voltage applied to the center tap of winding 15%.

Clutch controller 5'3 is adapted to channel current to either clutch 35or clutch 3'7 in accordance with the relative phasing between thevoltage of winding i6 3 and the voltage of alte nator The voltage ofalternator is applied to windings 156 and 158 of transformer 1554 withphasing in accordance with the usual dot convention. The center taps ofwindings 156 and 153 are connected to the collectors of transistors 162and laid, respectively. Ti e bases of transistor T52 and 16 5 areconnected through resistor 171 to the center tap of winding 16% andthrough resisters 17?: and 1'75 to the center taps of windings and 153.The anodes of diodes res, tea, 175i and 1172 are connected to the endsof windings 15d and The cathodes of diodes 16d and 372 are connectedthrough conducting member 17% to clutch 35. The cathodes of diodes 163and are connected through conductor 17? to clutch 37. The return currentpath from clutch 35 is through resistor in? and conductor 31 to thecenter tap of transformer winding res. The return current path fromclutch 37 is through resistor 16d and conductor Edi to the center tap ofwinding When the voltage of winding is in phase with the voltage ofwindings Add in accordance with the usual dot convention, the operationof clutch controller 53 is as follows. When the dot end of winding lot?is in the positive half-cycle, the current path to clutch 37 is from theemitter to the collector of transistor 162, through winding 15d, throughdiode through conductor 1'77 to clutch 1 7. The return path is throughresistor 169 and conductor 131 to the center tap of winding when the dotend of winding 150 is in the negative half-cycle, the current path toclutch is from the emitter to the collector of transistor Ed t, throughwinding i558, through diode 1%, through conwinding 26d.

When the voltage of winding is opposite in hase to the voltage ofwindings T56 and 155"; in accordance with the usual dot convention theoperation is as follows. i /hen the dot end winding is positive, thecurrent path to clutch 35 is from the emitter to the collector oftransistor res, through winding Edd, through diode 166, throughconductor 279 to clutch The return current path is through resistor T 7and conductor 131 to the center tap of vind res. During the halfcyclewhen the dot end of w ding res negative, the current path to clutch 55is from the emitter to the collector of transistor 16d, through winding158, through diod 1'72, through conductor 17% to clutch The returncurrent path is through resistor 16? and conductor 181 to the center tapof winding 16s.

It may thus be seen that when the voltage of winding 169 is in phasewith the voltage of winding 2 56 and 158, that clutch 37 is energizedand when the voltage of winding 16% is opposite in phase 0 the voltageof windings 3 .58, clutch 35 is energized. Resistors 173-, 175 and lilare provided to cause a quiescent current to flow through clutches 35and 37 when no signal ace-e911 "7 is applied. The quiescent currentwhich flows through clutches 35 37 causes equal and opposite torques tobe applied to the output of the servo system.

A typical magnetic particle clutch which is utilized in the preferredembodiment of this invention is shown in MG. 5. in FIG. 5, shaft 2% isthe output shaft of of the clutch and shaft is the input shaft. Clutchmember 25;; is adapted to rotate with shaft 2% while the remainingstructure, including the outer case, is adapted to rotate with shaft 232. Bearings are connected therebctwccn and are shown more particularlyat Electrical coil is wrapped around ferromagnetic spool 21% andreceives current from slip rings 212 and Elec omagnetic is generated inthe path shown by arrow i. o. Ferromagnetic particles are positionedwithin gaps and adapted to form chains to frictionally drive clutchmember to thereby transfer torque from shaft to shaft when coil Zilli isenergized.

The operation of the device of this invention under conditions whereinthe supporting vehicle is an airframe and inertial device ild is astabilized platform now follows.

In FlG. l, the device of this invention is shown with a supportingaircraft in level flight. It is to be noted that roll axis 3 ofreference device it? and roll axis 17 of the supporting aircraft nowcoincide. When the supporting aircraft 29 rolls about axis 1' somefriction is carried across bearings and 24- to cause gimbal 14 to moveaway from a right angle relative to gimbal l2. Assume for the momentthat the supporting aircraft rolls in the direction shown by arrow 1.Friction tends to move gimbal 1 3 in the same direction about axis 8 asthat followed by aircraft 2% about axis 1. However, reference deviceremains horizontal. Any attempt by gimbal 16 to roll with airframe 2%must be resisted by unwinding gimbal 1e tiereby to keep the plane ofgimbal at right angles to the plane of gimbal 12. Any misalignment froma right angle between the plane of gimbal l4- and the plane of gimbal 12causes synchro to generate a signal which energizes either clutch 35 orclutch 37 depending upon the direction of inclination of gimbal 12relative to gimbal M. The signal amplitude delivered to clutches 35 ordepends upon the angular deviation of the plane of gimbals 12 and 14from a right angle. A continuous servoing of the gimba 16 occurs.Giinbal 16 receives its energy from flywheel to lreep the planes ofgimbals l2 and l t normal to each other.

in FIG. 2, the supporting aircraft has pitched upward to an angle of theorder of 60 about pitch axis 15 and carries the gimbal lid with it.While the supporting aircraft is climbing, if it should roll about axis17, as shown by arrow 2, reference device ill maintains its stabilityand does not roll. H wever, rolling of the aircraft about axis If]causes motion of gimbal 16 about axis 8 (as shown by arrow 2) whichmoves gimbal 14 away from a right angle relative to gimbal 12. A signalis received from synchro which controls clutches and 37 (shown inFIG. 1) to transfer energy from flywheel 28 thereby to unroll gimba idin a direction contrary to that of arrow 1.

As the supporting aircraft passes through a vertical climb and pitchesover onto its back (as shown in FIG. 3), a slight roll of the aircraftin the direction of arrow It (and it is to be noted that the directionof arrow 1 relative to the aircraft has not changed from FIG. 2 to FIG.3) causes gimbal 16 to misalign gimbal 14 relative to gimbal 12 togenerate a signal in synchro 22 which should cause gimbal 16 to unwind.However, notice that a roll of the aircraft in the direction of arrow lin FIG. 2 causes gimbal 14 to move in the direction of arrow 2 aboutaxis b. After the aircraft has climbed through the vertical position (asin FIG. 3), however, a roll about axis 17 in the direction of arrow 1 bythe aircraft causes i gimbal 14- to go in the direction of arrow 3rather than arrow 2. 7

Since synchro 22 is continuously sensing errors due to roll of theaircraft, as the aircraft passes through the vertical position, a 180error signal is registered by synchro 22 which causes gimbal 16 to slewrapidly 180 about axes 11 and 17 in a very short period of time. Gimbal16 would actually appear to flip as the aircraft went through itsvertical.

With a typical gimbal system in which the device of this invention isfrequently utilized, the inertia load is of the order ofpoundinches-squared, the maximum velocity of gimbal 16 is required to beof the order of 12 radians-per-second, the maximum acceleration ofgimbal 16 is of the order of 300 radians-per-seconds uared with amaximum required torque on gimbal 16 of the order of 60 inch-pounds. Itis understood that these figures are by way of example only and are notlimiting on this invention.

In conventional servos, such requirements require heavy motors andamplifiers and prohibitive gear ratios. For example, in a conventionalservo for the load described above, an 80 to 1 gear ratio is notuncommon, the power consumption required for slewing gimbal 16 is of theorder of 200 watts and the weight of the motor and amplifier togetherwith the gear train is approximately 50 pounds.

In the device of this invention, the backlash is sub stantially zero,the average power consumption from the source which drives flywheel 23is of the order of 16 watts for the load described above, and the weightof the motor and amplifier is approximately 6 pounds.

It may thus be seen that considerable benefit is achieved when thedevice is to be used on a precision instrument and carried in anaircraft where instantaneous power requirements of high magnitude andheavy weight equipment are prohibitive.

The device of this invention then is a novel servo system which isadapted to rapidly slew devices such as gimbals, gun mounts, and likedevices which require high surges of instantaneous power.

The device of this invention has a relatively small average powerrequirement, small instantaneous sourcepower requirement, and is lightin weight.

Although the device of this invention has been described particularly inconnection with a roll gimbal in a servo system which is adapted todrive a roll follow up or redundant gimbal in an aircraft, it is notintended that the device should be limited to such a use nor should itbe limited by the above description which describes a specificembodiment, but only in accordance with the following claims.

We claim:

1. In combination: a gimbal mounted for rotation upon bearings; agyroscope supported by said gimbal, means for storing energy inmechanical form; and magnetic particle slip clutch means, connectedbetween said energy storing means and said gimbal to selectively apply atorque with a given value and sense to said gimbal.

2. In combination: a gimbal mounted upon bearings for rotation; agyroscope supported by said gimbal, flywheel means for storingmechanical energy; and slip clutch means connected between said meansfor storing energy and said gimbal adapted to selectively apply acontrolled torque to cause said gimbal to rotate in a controlleddirection with a controlled angular acceleration.

3. A device as recited in claim 2 in which said clutch means comprises:a pair of magnetic particle slip-clutches in torque opposition,connected to said gimbal by means of their output and having a commoninput connected to said flywheel means; means for selectively operatingonly one of said clutches at any particular time, the torque transmittedfrom said flywheel means to said ginibal being dependent in sense andmagnitude upon the signal applied to said clutch means.

4. In combination: a gimbal system including a redundant gimbal toprevent gimbal lock; a follow-up servo adapted to drive said redundantgimbal to prevent gimbal lock, said servo comprising mechanical energystoring means adapted to store mechanical energy, and clutch meansconnected between said mechanical energy storing means and saidredundant gimb'al to selectively cause said redundant gimbal to rotatein a controlled manner in a controlled direction.

5. A device as recited in claim 4 in which said mechanical energystoring means is a rotating mechanical member.

6. A device as recited in claim 4 in which said mechanical energystoring means is a mechanically rotating member and said clutch meanscomprises a pair of slip clutches having one end engaging said notatingmember and their other end mechanically opposing each other and attachedto said redundant gimbal to cause said gimbal to rotate.

7. In combination a girnbal system including at least one gimbal, agyroscope supported by said gimbal systern, servo means adapted to driveone of the gimbals in said gimbal system, said servo comprisingmechanical energy storing means adapted to store mechanical energy, andclutch means connected between said mechanical energy storing means andsaid one gimbal to selectively cause said one gimbal to rotate in acontrolled manner and in a controlled direction.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,692 Vickers Aug. 4, 1953 1,236,993 Sperry et al Aug. 14, 19172,386,402 Lilja Oct. 9, 1945 2,468,137 Tear Apr. 26, 1949 2,590,029Minorsky Mar. 18, 1952 2,758,484 Kel-tner Aug. 14, 1956 2,802,364Gievers Aug. 13, 1957 2,820,872 Carr Jan. 21, 1958 2,846,889 Ten Boschet a1 Aug. 12, 1958

